#include <stdio.h>
int jump(int n)
{
	if (n == 1)
		return 1;
	if (n == 2)
		return 2;
	else
		return jump(n - 1) + jump(n - 2);
 }

int main()
{
	int n = 0;
	scanf_s("%d", &n);
	int sum = jump(n);
	printf("%d", sum);
	return 0;
}